He said it would be “politically humiliating for a £2trillion economy”, would stop us making our own laws and subject us to Brussels rules for ever. He said: “This is not pragmatic, it is not a compromise. It is dangerous and unstable — politically and economically.

“This is not democracy. This is not what we voted for. This is an outrage. This is not taking back control; this is forfeiting control.”

He said Mr Gove’s suggestion that Chequers could be undone later was “total fantasy” and laid into Chancellor Mr Hammond’s Brexit doom-mongering.

The ex-Foreign Secretary's speech was given a positive reception from the crowd

And he ramped up the rhetoric by suggesting Mrs May risked being prosecuted under a 14th-century law saying that “no foreign court or government shall have jurisdiction in this country”.

Instead, he urged the Cabinet to force Theresa May to chuck Chequers and pursue a looser relationship with Brussels. And he had the crowd on their feet by warning: “If we get it wrong — if we bottle Brexit now — believe me, the people of this country will find it hard to forgive.

“I urge our friends in government to deliver what the people voted for, to back Theresa May in the best way possible — by softly, quietly, and sensibly backing her original plan.

“Because if we get it wrong we will be punished. And if we get it right we can have a glorious future. This Government will then be remembered for having done something brave and right and remarkable, and in accordance with the wishes of the people.”

Beyond Brexit, he gave a strong defence of his record as London Mayor and demanded the Tories pledge never to raise any taxes to see off the threat of Jeremy Corbyn’s Labour. In a direct attack on the PM, he blasted the party’s record on law and order.

He branded stop and search reforms championed by Mrs May when she was at the Home Office as “politically correct nonsense that puts lives at risk”.

And in a further headache for Downing Street, billionaire Tory party mega donor Sir Michael Hintze was also in the audience, alongside Mark Fullbrook, the business partner of Tory election guru Sir Lynton Crosby.

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She warned against ditching Chequers, saying it was the “only plan on the table at the moment” that would keep Northern Ireland as part of the United Kingdom.

She added: “He wanted to tear up our guarantee to the people of Northern Ireland.”

Another difficult day awaits her today as she gives her own speech to conference. And Ms Patel has already warned her: “Boris is the one they do want to hear.”

THE SUN SAYS: A BORIS BELTER

LOVE him or loathe him, Boris Johnson is our most charismatic politician and by far the best orator. Yesterday’s speech was electrifying and its argument hard to fault.

Last week a tedious line-up of droning Labour no-marks painted the bleakest possible picture of Britain. This week Tory ministers have delivered worthy but dull speeches to a half-empty hall.

Boris’s event had a two-hour queue. It was packed. And what he said stirred the blood of Tories and Leave voters — who stood, whooped and cheered.

He dismantled Corbyn’s “Tony Benn tribute act” and implored Tories to stand up confidently for THEIR values, not timidly ape Labour’s with more tax and suffocating state interference.

Taxes, he said, should be lower, not higher. Are you listening, Chancellor?

Boris rightly said affordable homes are the key to millennial hearts and to beating socialism again. That only the Tories will back businesses, “grafters, innovators and entrepreneurs” since Corbyn simply has no interest in them.

But the ex-Foreign Secretary’s attack on Theresa May’s Chequers offer to the EU was devastating.

All along, Brussels has focused on hobbling post-Brexit Britain as an independent trading nation. Chequers, Boris argued, lets them. It doesn’t “take back control” of our £2trillion economy. It hands it to the EU for ever.

That is even before Mrs May’s latest reported compromise, to stick to EU rules on goods indefinitely and all but end the chance of new trade deals.

What happened to the Prime Minister who stood defiant just a fortnight ago?

At this historic moment, Boris said, we must get Brexit right — and right now. A simple Canada-style free trade deal is the way, he says, not a Remainers’ charter cooked up in Downing Street.

Trouble is, neither has the votes to pass through the Commons. But the Tories shortly have to back one, or their self-destruction could gift Britain to the Marxists. And if that deal fails to meaningfully fulfil the Leave vote — with total control of our borders, laws, money AND trade — they are dead anyway.

So Mrs May has a huge speech today.

She must tell the country exactly why sticking with Chequers, her bewilderingly convoluted proposal rejected by the EU and seemingly hated by everyone outside No10, is our best option.